In the field of aircraft construction, it tends to be desirable to countersink predrilled holes in panels that are to be fastened to a structure to provide an airframe. This is performed so that the fastener used to fasten the panel to the structure may be flush with a surface of the panel (e.g. the outer surface of the aircraft). This tends to provide that the resulting airframe has better aerodynamic properties compared to if the fastener was not flush with the outer surface of the aircraft.
Countersinking of predrilled holes may be performed manually by human operators, e.g. using hand tools and workbenches. During the countersinking process, the panels may bend or deflect on the workbench due to the forces applied by the operator. The operator may manually compensate for such deflection. The operator may also compensate for curvature in the part being countersunk e.g. by manually adjusting the settings on the hand tool. However, large workforces and workspaces tend to be required for processing a large number of panels. Also, the human operators may develop repetitive strain injury caused by repeated drilling.
Countersinking of holes may also be performed using a machine tool (or robot). The use of such devices typically requires use a secure fixture that rigidly supports a panel so as to prevent it deflecting under the cutting/drilling forces. Such machine tools can be very expensive. The fixtures, which are usually required to be bespoke for the shape of panel being drilled, also tend to be expensive.